In terms of environmental pollution, the adverse effects of petroleum plastics has lead to increased use of bio-renewable and degradable bio-polyesters such as polylactic acid (PLA) and poly-hydroxyl butyrate (PHB). PLA has become a widely accepted resin in the plastics and packaging industries. The growing supply of PLA has enabled companies such as Nature Works, Naturally Iowa, and PepsiCo to manufacture and use “eco-friendly” water bottles and food packaging products. This growth is largely due to strong marketing of PLA's claimed environmental benefits and the reduced cost of PLA resin, which is now comparable to that of conventional polymers such as polyethylene. Despite being bio-renewable and biodegradable, the processability and mechanical properties of PLA have been major hurdles in the way of achieving widespread acceptance by industry. Concern regarding contamination of conventional plastic recycling streams has also resurfaced. These issues drive the need to develop a recycling method that would both improve the long-term viability of PLA as a renewable material and make it more attractive in terms of energy savings from increased reusability of PLA monomers.
Biodegradable PLA is made from renewable resources. This renewability makes PLA a good candidate for high volume disposable plastic products such as water bottles, milk jugs, and other food packaging applications. According to experts, the rise of corn ethanol as transportation fuel has increased the demand for corn grain that would otherwise be available for lactic acid production (Biodegradable Polymers and Plastics. Chiellini, Emo; Solaro, Roberto; Eds. (2003)). To make PLA a more successful commercial product, issues related to disposal of PLA (despite its biodegradable nature) need to be further addressed. Increasing the efficiency of PLA depolymerization would be significantly helpful to alleviate issues regarding PLA disposal by allowing the PLA to be recycled into its monomer. This would allow the material to be reused in food contact applications as well as eliminate the need of additional feedstock materials.
Accordingly, there is a need for economical sources of renewable monomers and biodegradable polymers. There is also a need for new and improved methods to recycle PLA, such that less energy is used in such processes than in currently available PLA recycling processes.